# [seqfan] Re: Middle digit in square numbers

Charles Greathouse charles.greathouse at case.edu
Mon Dec 12 19:28:39 CET 2016

```Lars, on the contribution page
https://oeis.org/Submit.html
https://oeis.org/edit/allocate
to allocate some A-numbers, which in my experience are always sequential.

Charles Greathouse
Case Western Reserve University

On Mon, Dec 12, 2016 at 5:18 AM, Lars Blomberg <larsl.blomberg at comhem.se>
wrote:

> OK.
>
> So 10 A-numbers will be needed.
> It would facilitate greatly if a sequence like Axxxxx0 .. Axxxxx9 could be
> allocated for this.
> Is that possible, if so, how?
> Regards,
> Lars Blomberg
>
> -----Ursprungligt meddelande-----
> Från: SeqFan [mailto:seqfan-bounces at list.seqfan.eu] För israel at math.ubc.ca
> Skickat: den 12 december 2016 08:39
> Till: Sequence Fanatics Discussion list <seqfan at list.seqfan.eu>
> Ämne: [seqfan] Re: Middle digit in square numbers
>
> Not at all too simple.  Please do contribute them.
>
> Cheers,
> Robert
>
> On Dec 11 2016, Lars Blomberg wrote:
>
> >
> >
> >Hello,
> >
> >
> >
> >Numbers k such that the middle digit of k^2 is d.
> >
> >Obviously k^2 must have an odd number of digits.
> >
> >
> >
> >Examples for d=4: 2^2 = 4, 12^2 = 144, 21^2 = 441, 29^2 = 841, 102 =
> >10404, ...
> >
> >
> >
> >Start of sequences for d =  0..9
> >
> >0: 10, 20, 30, 100, 105, 138, 145, .
> >
> >1: 1, 110, 119, 123, 127, 131, 142, .
> >
> >2: 11, 15, 18, 23, 25, 27, 101, 106,.
> >
> >3: 111, 124, 128, 139, 146, 156, 177, .
> >
> >4: 2, 12, 21, 29, 102, 107, 116, 120,.
> >
> >5: 16, 112, 150, 163, 166, 169, 172,.
> >
> >6: 13, 19, 31, 103, 108, 117, 121, .
> >
> >7: 24, 26, 113, 137, 144, 154, 181,.
> >
> >8: 17, 22, 28, 104, 109, 122, 126, .
> >
> >9: 3, 14, 114, 118, 130, 134, 148, .
> >
> >
> >
> >It was a surprise to me that none of these sequences are in OEIS.
> >
> >Maybe they are too simple to be included?
> >
> >
> >
> >/Lars Blomberg
> >
> >
> >
> >
> >--
> >Seqfan Mailing list - http://list.seqfan.eu/
> >
> >
>
>
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```